Start by placing a metal mixing bowl in the freezer for at least 15 minutes. This will ensure your whipped cream is extra fluffy.
Once your bowl is nicely chilled, add 4 tablespoons of sugar, 2 cups of heavy cream, and ½ teaspoon of vanilla extract. Mix these on high until thickened, which should take about 4 to 5 minutes. Once thickened, chill the mixture in the refrigerator until you're ready to use it.
Next, get a large skillet and mix together 1 cup of sugar, 3 tablespoons of cornstarch, and ¼ teaspoon of kosher salt over no heat. This will create a dry mixture that will serve as the base for your pudding.
Pour in 3 cups of whole milk into the dry mixture while using a whisk to fully incorporate and dissolve the sugar and cornstarch.
Next, whisk in 4 large egg yolks until fully combined. Then, stir in 3 tablespoons of chilled, cubed unsalted butter until melted and combined.
Now, turn the heat on to medium and cook the mixture while stirring frequently. Keep an eye on it and ensure you don't scramble the eggs. Cook until the mixture begins to thicken, which should take about 5 to 8 minutes. Once thickened, reduce the heat to low and stir constantly for one more minute. Finally, remove from heat and stir in 1½ teaspoons of vanilla extract.
Allow the pudding to cool slightly before transferring it to a bowl. Chill it in the refrigerator for about 2 to 3 hours; it will thicken even more as it cools.
In a separate metal mixing bowl, beat 4 large egg whites on medium speed until foamy. Gradually add ¼ teaspoon of cream of tartar and increase the speed to high. Beat until soft peaks form.
Add in ½ cup of sugar and ½ teaspoon of vanilla extract, continuing to beat until the peaks are just stiff. Be careful not to overmix, or the meringue might separate.
Now comes the fun part: assembling your Banana Pudding Trifle. Start with a layer of 50 to 70 vanilla wafers, followed by a layer of sliced 5 to 7 ripe bananas. Spread half of your whipped cream over the bananas.
Repeat the layering with another layer of wafers, bananas, and half of the pudding. Keep going with the remaining whipped cream and pudding.
Finish off with another layer of wafers and bananas, and use a spatula to spread all of the meringue on top. If you want to get fancy, you can use a kitchen torch to slightly brown the meringue for added flavor.
Finally, chill the assembled trifle for at least 4 hours, or overnight if you can resist. This allows all the flavors to meld beautifully.